Patch Test Using Arbitrary Incompatible Fluid and Solid Meshes on the FSI Boundary

A very important aspect of fluid-structure interaction analysis is the use of different meshes in the fluid and solid models. The reason is that often the fluid models require a much finer mesh than the solid models. Furthermore, the meshes at the fluid-solid interface may also not be compatible.

The most important test to assess incompatible finite element meshes is the patch test. The patch test verifies that constant tractions are properly transferred across incompatible meshes in both 2-D and 3-D.

One of the strengths of ADINA is its ability to handle totally different meshes and incompatible fluid-structure interfaces. A patch test in both 2-D and 3-D is shown below. The fluid is modeled with 3-node triangular elements in 2-D, and 4-node tetrahedral elements in 3-D. For the solid, 9-node quadrilateral elements in 2-D, and 27-node brick elements in 3-D are used. It can be seen that both pressure and stress are perfectly transferred across the fluid-solid interface.